🟡 Medium   ⏱ 5–30 min  Last verified: 20 May 2026

📖 ~1 min read

Table of contents
  1. Symptom & Impact
  2. Environment & Reproduction
  3. Root Cause Analysis
  4. Quick Triage
  5. Step-by-Step Diagnosis
  6. Solution – Primary Fix
  7. Solution – Alternative Approaches
  8. Verification & Acceptance Criteria
  9. Rollback Plan
  10. Prevention & Hardening
  11. Related Errors & Cross-Refs
  12. References & Further Reading

Symptom & Impact

Application latency rises on RHEL 9 after memory tuning changes related to THP and swappiness.

Environment & Reproduction

Higher response times, increased swap activity, and CPU spikes from memory compaction behavior.

Root Cause Analysis

Transparent Huge Pages mode and vm.swappiness values are misaligned with workload access patterns.

Quick Triage

Capture vmstat, sar, and application latency metrics before tuning to avoid guesswork.

Step-by-Step Diagnosis

Inspect THP mode and swappiness values, comparing against vendor guidance for your workload type.

Illustrative mockup for rhel-9 — rhel9-memory-tuning-baseline-49.webp
Collecting memory tuning baseline metrics for RHEL 9 workloads — Illustrative mockup — Progressive Robot

Solution – Primary Fix

Set sysctl/tuned changes incrementally, restart affected services, and monitor performance deltas.

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Illustrative mockup for rhel-9 — rhel9-tuned-sysctl-adjust-49.webp
Applying tuned profile and sysctl settings for memory behavior — Illustrative mockup — Progressive Robot

Solution – Alternative Approaches

Ensure tuned service is active and profiles are not overridden by conflicting startup scripts.

Verification & Acceptance Criteria

Use journalctl for kernel and memory-related messages that indicate reclaim or OOM pressure.

Rollback Plan

SELinux typically is not causal for these performance changes, but keep policy enforcing and audited.

Prevention & Hardening

Maintain reversible sysctl drop-ins and profile versions so you can revert quickly if latency worsens.

Compare post-change metrics to baseline over sustained load, not only brief spot checks.

Related tutorial: View the step-by-step tutorial for rhel-9.

View all rhel-9 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Apply memory tuning through staged performance tests and document workload-specific approved values.

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